Hand-held vital signs monitor

ABSTRACT

The invention features a vital sign monitor that includes: 1) a hardware control component featuring a microprocessor that operates as interactive, icon-driven GUI on an LCD; and, 2) a sensor component that connects to the control component through a shielded coaxial cable. The sensor features: 1) an optical component that generates a first signal; 2) a plurality electrical components (e.g. electrodes) that generate a second signal; and, 3) an acoustic component that generates a third signal. The microprocessor runs compiled computer code that operates: 1) the touch panel LCD; 2) a graphical user interface that includes multiple icons corresponding to different software operations; 3) a file-management system for storing and retrieving vital sign information; and 4) USB and short-range wireless systems for transferring data to and from the device to a PC.

CROSS REFERENCES TO RELATED APPLICATION

The present invention is a continuation of U.S. patent application Ser.No. 13/894,300, filed May 14, 2013, which is a continuation of U.S.patent application Ser. No. 11/470,708 filed Sep. 7, 2006, which issuedas U.S. Pat. No. 8,442,607, on May 14, 2013, which is herebyincorporated in its entirety including all tables, figures and claims.

FIELD OF THE INVENTION

The present invention relates to medical devices for monitoring vitalsigns, e.g. blood pressure.

DESCRIPTION OF THE RELATED ART

Pulse transit time (‘PTT’), defined as the transit time for a pressurepulse launched by a heartbeat in a patient's arterial system, has beenshown in a number of studies to correlate to both systolic and diastolicblood pressure. In these studies PTT is typically measured with aconventional vital signs monitor that includes separate modules todetermine both an electrocardiogram (ECG) and pulse oximetry. During aPTT measurement, multiple electrodes typically attach to a patient'schest to determine a time-dependent ECG characterized by a sharp spikecalled the ‘QRS complex’. This feature indicates an initialdepolarization of ventricles within the heart and, informally, marks thebeginning of the heartbeat. Pulse oximetry is typically measured with aclothespin-shaped device that clips to the patient's index finger, andincludes optical systems operating in both the red and infrared spectralregions. In addition to measuring a pulse oximetry value, this methodyields a time-dependent waveform, called a plethysmograph.Time-dependent features of the plethysmograph indicate both heart rateand a volumetric change in an underlying artery (e.g. in the finger)caused by the propagating pressure pulse.

In many studies PTT is calculated from the time separating the onset ofthe QRS complex to the foot of the plethysmograph. Alternatively, PTTcan be calculated as the time separating signals measured by two sensors(e.g. optical or pressure sensors), each sensitive to the propagatingpressure pulse, placed at different locations on the patient's body. Inboth cases, PTT depends primarily on arterial resistance, arterialcompliance, the propagation distance (closely approximated by thepatient's arm length), and of course blood pressure. Typically a highblood pressure results in a shorter PTT.

A number of issued U.S. Patents describe the relationship between PTTand blood pressure. For example, among others, U.S. Pat. Nos. 5,316,008;5,857,975; 5,865,755; and 5,649,543 each teach an apparatus thatincludes conventional sensors that measure an ECG and plethysmographthat are processed to measure PTT. U.S. Pat. Nos. 6,511,436; 6,599,251;and 6,723,054 each teach an apparatus that includes a pair of optical orpressure sensors, each sensitive to a propagating pressure pulse, thatmeasure PTT. As described in these patents, a microprocessor associatedwith the apparatus processes the PTT value to estimate blood pressure.

PTT-based measurements of blood pressure are complicated by a number offactors, one of which is the many time-dependent processes associatedwith each heartbeat that may correlate in a different way with bloodpressure, or in fact may not correlate at all. For example, prior to theinitial depolarization of the ventricles (marked by the QRS complex),the mitral valve opens and lets blood flow from the left atrium into theleft ventricle. This causes the ventricle to fill with blood andincrease in pressure. After the onset of the QRS, the mitral valvecloses and the aortic valve opens. When the heart contracts, bloodejects into the aorta until the aortic valve closes. The time separatingthe onset of the QRS and the opening of the aortic valve is typicallycalled the pre-injection period, or ‘PEP’. The time separating openingand closing of the aortic valve is called the left ventricular ejectionperiod, or ‘LVET’. LVET and PEP, along with additional time-dependentproperties associated with each heartbeat, are typically included in agrouping of properties called systolic time intervals, or ‘STIs’.

PTT and LVET can be measured with a number of different techniques, suchas impedance cardiography (‘ICG’) and by measuring a time-dependentacoustic waveform, called a phonocardiogram (‘PCG’), with an acousticsensor. The PCG, characterized by acoustic signatures indicating theclosing (and not opening) of the mitral and aortic valves, is typicallycoupled with an ECG to estimate PEP and LVET. For example, U.S. Pat.Nos. 4,094,308 and 4,289,141 each teach an apparatus that measures a PCGand ECG, and from these waveforms estimates PEP and LVET. U.S. Pat. No.7,029,447 teaches an apparatus using transit times calculated from anICG measurement to determine blood pressure.

Studies have also shown that a property called vascular transit time(‘VTT’), measured from features in both a PCG and plethysmograph, cancorrelate to blood pressure. Such a study, for example, is described inan article entitled ‘Evaluation of blood pressure changes using vasculartransit time’, Physiol. Meas. 27, 685-694 (2006). In addition, studieshave shown that PEP and LVET, taken alone, can correlate to bloodpressure. These studies typically require multiple sensors placed on thepatient's body to measure time-dependent waveforms that are processed todetermine PEP and LVET. Studies that relate these properties to bloodpressure, for example, are described in ‘Systolic Time Intervals inMan’, Circulation 37, 149-159 (1968); ‘Relationship Between SystolicTime Intervals and Arterial Blood Pressure’, Clin. Cardiol. 9, 545-549(1986); ‘Short-term variability of pulse pressure and systolic anddiastolic time in heart transplant recipients’, Am. J. Physiol. HeartCirc. Physiol. 279, H122-H129 (2000); and ‘Pulse transit time measuredfrom the ECG: an unreliable marker of beat-to-beat blood pressure’, J.Appl. Physiol. 100, 136-141 (2006).

SUMMARY OF THE INVENTION

To address any deficiencies in the prior art, the present inventionprovides a hand-held vital signs monitor that combines a cuffless,PTT-based measurement of blood pressure in a device that has many of thefeatures of a conventional personal digital assistant (‘PDA’). Themonitor, for example, includes a microprocessor that runs an icon-drivengraphical user interface (‘GUI’) on a color, liquid crystal display(‘LCD’) attached to a touch panel. A user selects different measurementmodes, such as continuous, one-time, and 24-hour ambulatory modes, bytapping a stylus on an icon within the GUI. The monitor also includesseveral other hardware features commonly found in PDAs, such asshort-range (e.g., Bluetooth® and WiFi®) and long-range (e.g., CDMA,GSM, IDEN) modems, global positioning system (‘GPS’), digital camera,and barcode scanner.

The monitor makes cuffless blood pressure measurements using a sensorthat includes small-scale optical, electrical, and acoustic sensors. Thesensor typically attaches to a patient's chest, just below their sternalnotch. A flexible foam substrate supports the optical, electrical, andacoustic sensors and has a form factor similar to a conventionalbandaid. During operation, these sensors measure, respectively,time-dependent optical, electrical and acoustic waveforms that themicroprocessor then analyzes as described in detail below to determineblood pressure and other vital signs. In this way, the sensor replaces aconventional cuff to make a rapid measurement of blood pressure withlittle or no discomfort to the patient.

Specifically, in one aspect, the invention features a vital sign monitorthat includes: 1) a hardware control component featuring amicroprocessor that operates an interactive, icon-driven GUI on an LCD;and, 2) a sensor component that connects to the control componentthrough a shielded coaxial cable. The sensor features: 1) an opticalcomponent that generates a first signal; 2) a plurality electricalcomponents (e.g. electrodes) that generate a second signal; and, 3) anacoustic component that generates a third signal. The microprocessorruns compiled computer code that operates: 1) the touch panel LCD; 2) agraphical user interface that includes multiple icons corresponding todifferent software operations; 3) a file-management system for storingand retrieving vital sign information; and 4) USB and short-rangewireless systems for transferring data to and from the device to a PC.The monitor can include removable memory components for storing andtransporting information. For example, these components can be a flashcomponent or a synchronous dynamic random access memory (SDRAM) packagedin a removable chip.

In other embodiments, the vital signs monitor includes a barcode scannerthat reads barcodes corresponding to both patients and in-hospitaloperators. The monitor can also include a digital camera for taking andstoring photographs, and a location-determining component (e.g. a globalpositioning system, or GPS) for determining the patient's location. Thevital signs monitor can communicate with external devices throughwireless modems that operate both short-range and long-range wirelessprotocols. Specifically, these modems may operate on: 1) a wide-areawireless network based on protocols such as CDMA, GSM, or IDEN; and, 2)a local-area wireless network based on a protocols such as 802.11,802.15, 802.15.4. These protocols allow the vital signs monitor tocommunicate with an external computer, database, or in-hospitalinformation system.

The vital signs monitor works in concert with the sensor to measure apatient's vital signs without using a convention blood pressure cuff.The patient typically wears the sensor on or just below the ‘sternal’notch of their chest, proximal to their heart. In this location thesensor simultaneously measures, optical, electrical, and acousticsignals, which are then processed with an algorithm described below tomeasure blood pressure and other vital signs. The measurement ispossible because: 1) the proximity of this area to the heart allows theacoustic sensor to measure the acoustic waveform; 2) an abundance ofcapillaries in the sternal notch, meaning the optical waveform can bemeasured in a reflective mode; and 3) the strong electrical activity ofthe heart in this area, meaning the electrical waveform can be measuredwith a high signal-to-noise ratio even when the electrodes arerelatively close together.

In embodiments, to generate the optical waveform, the optical sensorirradiates a first region with a light source (e.g. an LED), and thendetects radiation reflected from this region with a photodetector. Thesignal from the photodetector passes to an analog-to-digital converter,where it is digitized so that it can be analyzed with themicroprocessor. The analog-to-digital converter can be integrateddirectly into the microprocessor, or can be a stand-alone circuitcomponent. Typically the radiation from the light source has awavelength in a ‘green’ spectral region, typically between 520 and 590nm. Alternatively, the radiation can have a wavelength in the infraredspectral region, typically between 800 and 1100 nm. To detect thisradiation, the optical sensor includes a light detector, e.g. aphotodiode or phototransistor. In preferred embodiments the light sourceand the light detector are included in the same housing or electronicpackage.

To generate the electrical waveform, the electrical sensor detects firstand second electrical signals with, respectively, first and secondelectrodes. The electrical signals are then processed (e.g. with amulti-stage differential amplifier and band-pass filters) to generate atime-dependent electrical waveform similar to an ECG. The electricalsensor typically includes a third electrode, which generates a groundsignal or external signal that is further processed to, e.g., reducenoise-related artifacts in the electrical waveform. In embodiments, theelectrodes are disposed on opposite ends of the substrate, and aretypically separated by a distance of at least 5 cm. In otherembodiments, to improve the signal-to-noise ratio, the sensor includes athird electrode connected to the electrical sensor by a cable. In otherembodiments, the electrodes include an Ag/AgCl material (e.g., anAg/AgCl paste sintered to a metal contact) and a conductive gel.Typically a first surface of the conductive gel contacts the Ag/AgClmaterial, while a second surface is covered with a protective layer. Theprotective layer prevents the gel from drying out when not in use, andtypically has a shelf life of about 24 months. In still otherembodiments, the electrodes are made from a conductive material such asconductive rubber, conductive foam, conductive fabric, and metal.

To generate the acoustic waveform, the acoustic sensor typicallyincludes a microphone or piezoelectric device that measureslow-frequency pressure waves (e.g. sounds) from the user's heart. Thisresults in a time-dependent acoustic waveform that typically includestwo unique ‘packets’ comprised of frequency components typically rangingfrom 40-500 Hz. The packets correspond to closing of the mitral andaortic valves. The acoustic sensor can also contact a non-conductiveimpedance-matching gel, such as Vaseline®, to decrease acousticreflections at the skin/sensor interface. This typically increases themagnitude of the measured acoustic waveform.

During a measurement, the processor analyzes the various waveforms todetermine one or more time-dependent parameters, e.g. VTT, PTT, PEP, orLVET, which are then further processed to determine blood pressure. Theprocessor can further process a waveform, e.g. take a second derivativeor ‘fit’ the rise or fall times of the optical waveform with amathematical function, to determine additional properties relating toblood pressure. For example, in one embodiment, the microprocessordetermines at least one parameter by analyzing a first point from apulse within the optical waveform and a second point from a featurerepresenting a heart sound within the acoustic waveform (to estimateVTT). In another embodiment, the processor determines a second parameterby analyzing a point from a QRS complex within the electrical waveformand a point from either a pulse within the optical waveform (to estimatePTT) or a point within the acoustic waveform (to estimate PEP). In yetanother embodiment, the processor analyzes points representing two heartsounds from the acoustic waveform to estimate LVET.

Once these parameters are determined, the processor analyzes them with amathematical model to determine the user's blood pressure. For example,the processor can process one or more parameters with a linear model,characterized by a slope and a y-intercept, to relate it (or them) to ablood pressure value. Alternatively, the processor can relate one ormore parameters to blood pressure using a relatively complex model, suchas one that includes a polynomial, exponential, or a non-linear set ofequations. Once the various parameters are related to blood pressure,several ‘sub-values’ can be determined and concatenated into a singleblood pressure value using, e.g., a pre-determined weighted average. Theabove-mentioned models can also use calibration values, e.g. calibrationvalues from a cuff-based system or arterial line, to increase theaccuracy of the blood pressure calculation.

The invention has a number of advantages. In general, the monitorcombines all the data-analysis features and form factor of aconventional PDA with the monitoring capabilities of a conventionalvital sign monitor. This results in an easy-to-use, flexible monitorthat performs one-time, continuous, and ambulatory measurements both inand outside of a hospital. And because it lacks a cuff, the monitormeasures blood pressure in a simple, rapid, pain-free manner.Measurements can be made throughout the day with little or noinconvenience to the user. Moreover, the optical, electrical, andacoustic sensors are integrated on a single substrate connected to thecontrol module with a single wire. This means vital signs and relatedwaveforms, such as blood pressure, heart rate, ECG, opticalplethysmograph, and respiration rate, can be measured with a minimalamount of wires and patches connected to the patient. This can make thepatient more comfortable, particularly in a hospital setting.

These and other advantages are described in detail in the followingdescription, and in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B show front and top views of a vital signs monitoraccording to the invention;

FIG. 2 shows a top view of a sensor that measures vital signs with themonitor of FIGS. 1A and 1B and includes optical electrical and acousticsensors supported by a flexible substrate;

FIGS. 3A and 3B show, respectively, bottom and top views of a circuitboard within the vital signs monitor of FIGS. 1A and 1B;

FIGS. 4A and 4B show screen captures taken from a color LCD of FIG. 3Bthat features an icon-driven GUI;

FIG. 5 shows a schematic view of an embedded software architecture usedin the vital signs monitor of FIGS. 1A and 1B;

FIG. 6 shows a schematic view of the vital sign monitor of FIGS. 1A and1B and the sensor of FIG. 2 measuring a patient near their sternalnotch; and,

FIG. 7 shows a schematic view of an Internet-based system used to sendinformation from the vital signs monitor of FIGS. 1A and 1B to theInternet and an in-hospital information system.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1A, 1B, and 2 show a vital signs monitor 10 according to theinvention that attaches through a connector 4 and coaxial cable 27 to asensor 20 that measures systolic and diastolic blood pressure, heartrate, respiratory rate, and ECG. Using a plastic stylus 11, an operatorcontrols the vital signs monitor 10 through a GUI (shown in FIGS. 4A and4B) that runs on a LCD/touch panel assembly 35. In this way, theoperator can easily select a variety of different measurement modes tocharacterize a patient. For example, using the GUI and LCD/touch panelassembly 35, the user can select modes for one-time and continuousmeasurements in the hospital, as well as 24-hour ambulatory measurementsand measurements made during patient transport outside of the hospital.

A plastic housing 60 surrounds the monitor 10 to protect its internalcomponents. The monitor 10 additionally includes a barcode reader 2 tooptically scan patient information encoded, e.g., on a wrist-wornbarcode. A port 3 receives an external thermometer that measures apatient's esophageal temperature. The monitor 10 is lightweight,hand-held, and additionally mounts to stationary objects within thehospital, such as beds and wall-mounted brackets, through mounting holeson its back panel 13.

Referring to FIG. 2, the sensor 20 includes an adhesive foam substrate21 that mounts a reflective optical sensor 25, piezoelectric acousticsensor 26, and an electrical sensor featuring a primary electrode 23 a,reference electrode 23 b, and ground electrode 23 c. These sensorsmeasure, respectively, optical, acoustic, and electrical waveforms.During operation, analog electrical signals from each sensor 23 a-c, 25,and 26 pass through a tab connector 22 that connects to the coaxialcable 27, and then through the cable 27 to an analog-to-digitalconverter mounted on a circuit board (shown in FIG. 3A) within thehousing 60. The analog-to-digital converter digitizes these signals togenerate digital waveforms, which the microprocessor then processes withan algorithm to measure blood pressure.

To reduce the effects of ambient light, the optical sensor 25 is mountedtowards the middle of the foam substrate 21 and includes alight-emitting diode (LED) that typically emits green radiation(λ=520-570 nm) and a photodetector that measures reflected opticalradiation which varies in intensity according to blood flow inunderlying capillaries. The optical sensor 25 typically includes theLED, photodetector, and a small-scale amplifier in the same package; apreferred sensor is model TRS1755 manufactured by TAOS, Inc. of Plano,Tex. During operation, the photodetector generates a photocurrent inresponse to the reflected radiation, which the amplifier furtheramplifies before the signal passes through the tab connector 22 andcoaxial cable 27. The resultant signal is similar to a conventionalplethysmograph measured from a finger using a pulse oximeter.

The piezoelectric acoustic sensor 16 detects sounds waves following eachof the patient's heartbeats to generate an acoustic waveform, alsocalled a phonocardiogram. The acoustic waveform features two ‘beats’that each includes a collection of acoustic frequencies. The first andsecond beats represent sounds made following closure of, respectively,the heart's mitral and aortic valves; these are the conventional ‘lub’and ‘dub’ heard through a stethoscope. The preferred piezoelectricacoustic sensor is a Condenser Microphone Cartridge (manufacturer:Panasonic; part number: WM-55D103).

Concurrent with measurement of the optical and acoustic waveforms, theprimary 23 a, reference 23 b, and ground 23 c electrodes in the sensor20 detect an electrical impulse generated in the patient following aheartbeat. This signal, which is similar to that collected with aconventional 2-lead ECG system, is registered as an analog voltage whichis then digitized by the analog-to-digital converter to form theelectrical waveform. The primary 23 a and reference 23 b electrodes aretypically spaced by at least 2.5 cm to generate an electrical signalwith an acceptable signal-to-noise ratio; the ground electrode 23 cshould be disposed at least 1 cm away from either the primary 23 a orreference 23 b electrode. Typically each of the electrodes includes ametal pad (e.g., a thin silver film) deposited directly on the foamsubstrate 21. To effectively measure electrical signals from thepatient, the metal pad is typically coated with a thin layer of Ag/AgCl,which is then covered by a conductive adhesive gel.

FIGS. 3A and 3B show a circuit board 29 mounted within the vital signsmonitor that supports a variety of circuit elements required for themonitor to exhibit PDA-like functionality while measuring blood pressureas described above. A rechargeable lithium-ion battery 6 (manufacturer:Varta Microbattery; part number: 3P/PLF 503562 C PCM W) powers each ofthe circuit elements and is controlled by a conventional on/off switch13. A smaller back-up battery 28 is used to power volatile memorycomponents. All compiled computer code that controls the monitor'svarious functions runs on a high-end microprocessor 39, typically an ARM9 (manufacturer: Atmel; part number: AT91SAM9261-CJ), that is typicallya ‘ball grid array’ package mounted underneath an LCD display 35. Beforebeing processed by the microprocessor 39, analog signals from theoptical, acoustic, and electrical sensors pass through a connector 4 tothe analog-to-digital converter 41, which is typically a separateintegrated circuit (manufacturer: Texas Instruments; part number:ADS8344NB) that digitizes the waveforms with 16-bit resolution. Suchhigh resolution is typically required to adequately process the optical,acoustic, and electrical waveforms, as described in more detail below.The microprocessor 39 also controls a pulse oximetry circuit 12including a connector (not shown in the figure) that connects to anexternal pulse oximetry finger sensor. To measure temperature, a probecontaining a temperature-sensitive sensor (e.g. a thermistor) connectsthrough a stereo jack-type connector 4, which in turn connects to theanalog-to-digital converter 41. During operation, thetemperature-sensitive sensor generates an analog voltage that varieswith the temperature sensed by the probe. The analog voltage passes tothe analog-to-digital converter 41, where it is digitized and sent tothe microprocessor 39 for comparison to a pre-determined look-up tablestored in memory. The look-up table correlates the voltage measured bythe temperature probe to an actual temperature.

After calculating vital signs, the microprocessor 39 displays them onthe LCD 35 (manufacturer: EDT; part number: ER05700NJ6*B2), whichadditionally includes a touch panel 36 on its outer surface, and abacklight 37 underneath. An LCD control circuit 15 includes ahigh-voltage power supply that powers the backlight, and an LCDcontroller that processes signals from the touch panel 37 to determinewhich coordinate of the LCD was contacted with the stylus. Themicroprocessor 39 runs software that correlates coordinates generated bythe LCD controller with a particular icon (see, e.g., FIGS. 5A and 5B),and ultimately to software functions coded into the microprocessor 39.

Information can be transferred from the monitor to an external deviceusing both wired and wireless methods. For wired transfer ofinformation, the circuit board 29 includes a universal serial bus (USB)connector 16 that connects directly to another device (e.g. a personalcomputer), and a removable SD flash memory card 14 that functions as aremovable storage medium for large amounts (e.g., 1 GByte and larger) ofinformation. For wireless transfer of information, the circuit board 29includes both a short-range Bluetooth® transceiver 18 that sendsinformation over a range of up to 30 meters (manufacturer: BlueRadios;part number: BR-C40A). The Bluetooth® transceiver 18 can be replacedwith a transceiver that operates on a wireless local-area network, suchas a WiFi® transceiver (manufacturer: DePac; part number:WLNB-AN-DP101). For long-range wireless transfer of information, thecircuit board 29 includes a CDMA modem 9 (manufacturer: Wavecom; partnumber: Wismo Quik WAV Q2438F-XXXX) that connects through a thin,coaxial cable 19 to an external antenna 41. The CDMA modem 9 can bereplaced with a comparable long-range modem, such as one that operateson a GSM or IDEN network.

The circuit board 29 includes a barcode scanner 2 (manufacturer: Symbol;part number: ED-95S-I100R) that can easily be pointed at a patient toscan their wrist-worn barcode. The barcode scanner 2 typically has arange of about 5-10 cm. Typically the barcode scanner 2 includes aninternal, small-scale microprocessor that automatically decodes thebarcode and sends it to the microprocessor 39 through a serial port foradditional processing.

A small-scale, noise-making piezoelectric beeper 31 connects to themicroprocessor 39 and sounds an alarm when a vital sign value exceeds apre-programmed level. A small-scale backup battery 33 powers a clock(not shown in the figure) that sends a time/date stamp to themicroprocessor 39, which then includes it with each stored data file.

FIGS. 4A and 4B show screen captures of first and second softwareinterfaces 43, 51 within the graphical user interface that run on theLCD 35. Referring to FIG. 4A, the first software interface 43 functionsas a ‘home page’ and includes a series of icons that perform differentfunctions when contacted through the touch panel with the stylus. Thehome page includes icons for ‘quick reading’, which takes the userdirectly to a measurement screen similar to that shown in the secondsoftware interface 51, and ‘single reading’, which allows the user toenter patient information (e.g. the patient's name and biometricinformation) before taking a measurement. Information is entered eitherdirectly using a soft, on-screen QWERTY touch-keyboard, or by using thebarcode scanner. The home page also includes a ‘monitor’ icon which,when initiated, allows the monitor to continuously measure bloodpressure and other vital signs and send them through either the short orlong-range wireless transmitter to an external device (e.g., a personalcomputer located at a nursing station).

The home page additionally includes a ‘user’ icon that allows the userto enter their information through either the soft keyboard or barcodescanner. Settings on the device, e.g. alarm values for each vital signand periodicity of measurements made during the continuous ‘monitor’mode, are adjusted using the ‘setup’ icon. Using the ‘connect’ icon theuser can send information from the monitor to the external device usingeither USB or the short-range wireless transmitter. Information can bestored and recalled from memory using the ‘memory’ icon, and can beanalyzed with a variety of statistical algorithms using the ‘stats’icon. The ‘help’ icon renders graphical help pages for each of theabove-mentioned functions.

The second software interface 51 shown in FIG. 4B is rendered after theuser initiates the ‘single reading’ icon in first software interface 43of FIG. 5A. This interface shows the patient's name (entered usingeither the soft keyboard or barcode scanner) and values for theirsystolic and diastolic blood pressure, heart rate, pulse oximetry, andtemperature. The values for these vital signs are typically updatedevery few seconds. In this case the software interface 51 shows anoptical waveform (labeled ‘PPG’) measured with the optical sensor, andan acoustic waveform (labeled ‘PCG’) measured with the acoustic sensor.These waveforms are continually updated on the LCD 35 while the sensoris attached to the patient. The second software interface 51additionally includes smaller icons at the bottom of the LCD 35 thatcorrespond to, respectfully, the date, time, and remaining battery life.The ‘save’ icon saves all the current vital sign and waveforminformation displayed measured by the monitor to an on-board memory,while the ‘home’ icon renders the first software interface 43 shown inFIG. 5A.

FIG. 5 shows a software architecture 80 that runs on the above-describedmicroprocessor, allowing the monitor to measure vital signs and operateall the electrical components shown in FIGS. 3A and 3B, and run theGraphical User interface (GUI) 64 shown in FIGS. 4A and 4B. The softwarearchitecture 80 is based on an operating system 60 called the μC/OS-II(vendor: Micrium) which is loaded onto the microprocessor and operatesin conjunction with software libraries (vendor: Micrium) for the GUI 64.The USB 66 library (vendor: Micrium) operates the transfer of storedpatient vital signs data through a USB cable to external devices. AMicrosoft Windows® compatible FAT32 embedded file management system (FS)68 is a read-write information allocation library that stores allocatedpatient information and allows retrieval of information through the GUI64. These libraries are compiled along with proprietary data acquisitioncode 62 library that collects of digitized waveforms and temperaturereadings from the analog-to-digital converter and stores them into RAM.The event processor 72 is coded using the Quantum Framework (QF)concurrent state machine framework (vendor: Quantum Leaps). This allowseach of the write-to libraries for the GUI 64, USB 66, file system 68,and data acquisition 62 to be implemented as finite state machines(‘FSM’), e.g. a GUI FSM 76, USB FSM 78, and file system FSM 79. Each FSM76, 78, and 79 structure allows the user to react to an event on the GUI64 screen during the measurement process or data retrieval. For example,the algorithm that calculates blood pressure from waveforms receivedthrough the data acquisition library 62 is implemented as an algorithmFSM 74. Each FSM 74, 76, 78, and 79 communicates with a software eventprocessor 72 through a software protocol called ‘concurrent FSMabstraction’ 70. Using this architecture 80, the algorithm FSM 74, GUIFSM 76, USB FSM 78, and file system FSM 79 are implemented usinglow-level code included in the associated software libraries.

Referring to FIG. 6, during operation, a patient's vital signs aremeasured while the monitor 10 is typically held by a medicalprofessional or mounted on a bracket while the sensor 20 is adhered tothe patient's chest. In this way, the sensor 20 is proximal to thepatient's heart 86, a location that allows it to simultaneously measureoptical, electrical, and acoustic activity that follows each heartbeatto generate the time-dependent analog waveforms described above. Thewaveforms propagate through shielded, co-axial wires in a cable 90 thatconnects the sensor 20 to the monitor 10. There, hardware and softwarewithin the monitor process the information to measure the patient'svital signs. Pulse oximetry measurements are typically made by attachinga standard pulse oximeter sensor to the patient's finger, and processingmeasured information the pulse oximetry circuit described with referenceto FIG. 3A. Determining pulse oximetry in this way is a standardpractice known in the art, and is described, for example, in U.S. Pat.No. 4,653,498 to New, Jr. et al., the contents of which are incorporatedherein by reference.

In addition to those methods described above, a number of additionalmethods can be used to calculate blood pressure from the optical,electrical, and acoustic waveforms. These are described in the followingco-pending patent applications, the contents of which are incorporatedherein by reference: 1) CUFFLESS BLOOD-PRESSURE MONITOR AND ACCOMPANYINGWIRELESS, INTERNET-BASED SYSTEM (U.S. Ser. No. 10/709,015; filed Apr. 7,2004); 2) CUFFLESS SYSTEM FOR MEASURING BLOOD PRESSURE (U.S. Ser. No.10/709,014; filed Apr. 7, 2004); 3) CUFFLESS BLOOD PRESSURE MONITOR ANDACCOMPANYING WEB SERVICES INTERFACE (U.S. Ser. No. 10/810,237; filedMar. 26, 2004); 4) VITAL SIGN MONITOR FOR ATHLETIC APPLICATIONS (U.S.Ser. No.; filed Sep. 13, 2004); 5) CUFFLESS BLOOD PRESSURE MONITOR ANDACCOMPANYING WIRELESS MOBILE DEVICE (U.S. Ser. No. 10/967,511; filedOct. 18, 2004); and 6) BLOOD PRESSURE MONITORING DEVICE FEATURING ACALIBRATION-BASED ANALYSIS (U.S. Ser. No. 10/967,610; filed Oct. 18,2004); 7) PERSONAL COMPUTER-BASED VITAL SIGN MONITOR (U.S. Ser. No.10/906,342; filed Feb. 15, 2005); 8) PATCH SENSOR FOR MEASURING BLOODPRESSURE WITHOUT A CUFF (U.S. Ser. No. 10/906,315; filed Feb. 14, 2005);9) PATCH SENSOR FOR MEASURING VITAL SIGNS (U.S. Ser. No. 11/160,957;filed Jul. 18, 2005); 10) WIRELESS, INTERNET-BASED SYSTEM FOR MEASURINGVITAL SIGNS FROM A PLURALITY OF PATIENTS IN A HOSPITAL OR MEDICAL CLINIC(U.S. Ser. No. 11/162,719; filed Sep. 9, 2005); 11) HAND-HELD MONITORFOR MEASURING VITAL SIGNS (U.S. Ser. No. 11/162,742; filed Sep. 21,2005); 12) CHEST STRAP FOR MEASURING VITAL SIGNS (U.S. Ser. No.11/306,243; filed Dec. 20, 2005); 13) SYSTEM FOR MEASURING VITAL SIGNSUSING AN OPTICAL MODULE FEATURING A GREEN LIGHT SOURCE (U.S. Ser. No.11/307,375; filed Feb. 3, 2006); 14) BILATERAL DEVICE, SYSTEM AND METHODFOR MONITORING VITAL SIGNS (U.S. Ser. No. 11/420,281; filed May 25,2006); and 15) SYSTEM FOR MEASURING VITAL SIGNS USING BILATERAL PULSETRANSIT TIME (U.S. Ser. No. 11/420,652; filed May 26, 2006).

FIG. 7 shows an example of a computer system 200 that operates inconcert with the monitor 10 to send information from a patient 85 to anexternal computer 205, 211. When the patient is ambulatory the monitor10 can be programmed to send information to a website 206 hosted on theInternet. For example, using an internal wireless modem, the monitor 10sends information through a series of towers 201 in a nation-widewireless network 202 to a wireless gateway 203 that ultimately connectsto a host computer system 205. The host computer system 205 includes adatabase 204 and a data-processing component 208 for, respectively,storing and analyzing data sent from the device. The host computersystem 205, for example, may include multiple computers, softwaresystems, and other signal-processing and switching equipment, such asrouters and digital signal processors. The wireless gateway 203preferably connects to the wireless network 202 using a TCP/IP-basedconnection, or with a dedicated, digital leased line (e.g., a VPN,frame-relay circuit or digital line running an X.25 or other protocols).The host computer system 205 also hosts the web site 206 usingconventional computer hardware (e.g. computer servers for both adatabase and the web site) and software (e.g., web server, applicationserver, and database software).

To view information remotely, the patient or medical professional canaccess a user interface hosted on the web site 206 through the Internet207 from a secondary computer system such as an Internet-accessible homecomputer. The computer system 200 may also include a call center,typically staffed with medical professionals such as doctors, nurses, ornurse practitioners, whom access a care-provider interface hosted on thesame website 206.

Alternatively, when the patient is in the hospital, the monitor can beprogrammed to send information to an in-hospital information system 211(e.g., a system for electronic medical records). In this case, themonitor 10 sends information through an in-hospital wireless network 209(e.g., an internal WiFi® network) that connects to a desktop applicationrunning on a central nursing station 210. This desktop application 210can then connect to an in-hospital information system 211. These twoapplications 210, 211, in turn, can additionally connect with eachother. Alternatively, the in-hospital wireless network 209 may be anetwork operating, e.g. a Bluetooth®, 802.11a, 802.11b, 802.1g,802.15.4, or ‘mesh network’ wireless protocols that connects directly tothe in-hospital information system 211. In these embodiments, a nurse orother medical professional at a central nursing station can quickly viewthe vital signs of the patient using a simple computer interface.

Other embodiments are also within the scope of the invention. Forexample, software configurations other than those described above can berun on the monitor to give it a PDA-like functionality. These include,for example, Micro C OS®, Linux®, Microsoft Windows®, embOS, VxWorks,SymbianOS, QNX, OSE, BSD and its variants, FreeDOS, FreeRTOX, LynxOS, oreCOS and other embedded operating systems. The monitor can also run asoftware configuration that allows it to receive and send voice calls ortext messages through its embedded long-range modem. This information,for example, can be used to communicate with a patient in a hospital orat home. In other embodiments, the monitor can connect to anInternet-accessible website to download content, e.g. calibrations, textmessages, and information describing medications, from an associatedwebsite. As described above, the monitor can connect to the websiteusing both wired (e.g. USB port) or wireless (e.g. short or long-rangewireless transceivers) means.

In still other embodiments, the optical, electrical, and acousticwaveforms can be processed to determine other vital signs. For example,relatively low-frequency components of an ‘envelope’ describing both theelectrical and optical waveforms can be processed to determinerespiratory rate. This can be done, for example, using an analysistechnique based on Fourier Transforms. In other embodiments, thesubstrate can be modified to include light sources (e.g. LEDs) operatingin both the red (e.g. λ=600-700 nm) and infrared (λ=800-900 nm) spectralregions. With these modifications, using techniques known in the art,that substrate can potentially measure pulse oximetry in areflection-mode configuration. In still other embodiments,time-dependent features from the PCG can be analyzed to determinecardiac properties such as heart murmurs, lung sounds, and abnormalitiesin the patient's mitral and aortic valves.

Still other embodiments are within the scope of the following claims.

We claim as our invention:
 1. A hand-held vital signs system,comprising: a housing comprising a microprocessor that is operablyconnected to a touch screen display on a surface of the housing toprovide operation controls for the vital signs system on an icon-drivengraphical user interface; at least two electrodes operably connected tothe microprocessor configured to measure an electrical signal which isprocessed by the microprocessor to provide an ECG waveform; and a firstsensor operably connected to the microprocessor configured to measure alow-frequency waveform comprising frequency components of between 40 Hzand 500 Hz indicative of heart valve operation; a second sensor operablyconnected to the microprocessor configured to measure an opticalwaveform, wherein the microprocessor is configured to collectivelyprocess the low-frequency waveform and the ECG waveform to determine apre-ejection period, to collectively process the optical waveform, theECG waveform and the pre-ejection period to determine a vascular transittime, and to determine a blood pressure value using the vascular transittime.
 2. A hand-held vital signs system according to claim 1, whereinthe system further comprises a wireless communications system configuredfor wireless transfer of information from the microprocessor to anexternal device.
 3. A hand-held vital signs system according to claim 2,wherein the wireless communications system communicates with theexternal device by one or more of a Bluetooth protocol, a WiFi protocol,a CDMA protocol, a GSM protocol, and an IDEN protocol.
 4. A hand-heldvital signs system according to claim 1, wherein the at least twoelectrodes and the second sensor are disposed on a surface of thehousing.
 5. A hand-held vital signs system according to claim 1, whereincalibration information is used by the microprocessor duringdetermination of the blood pressure value to account for arterialproperties of a user of the vital signs system.
 6. A hand-held vitalsigns system according to claim 1, wherein the first sensor is apiezoelectric sensor.